CNC lathes are one of the most widely used CNC machine tools. They are mainly used for cutting and processing of inner and outer cylindrical surfaces of shaft parts or disk parts, inner and outer conical surfaces of arbitrary cone angles, complex rotating inner and outer curved surfaces, and cylindrical and conical threads, and can perform grooving, drilling, reaming, reaming and boring, etc.
CNC machine tools automatically process the parts to be processed according to the pre-compiled processing program. We compile the processing route, process parameters, tool motion trajectory, displacement, cutting parameters and auxiliary functions of the parts into a processing program sheet according to the instruction code and program format specified by the CNC machine tool of the CNC lathe customization manufacturer, and then record the contents of this program sheet on the control medium, and then input it into the CNC device of the CNC machine tool, so as to command the machine tool to process parts.
Semi-closed-loop control system refers to the installation of angular displacement and angular velocity detection devices at the end of the motor shaft or screw rod, which are fed back to the comparator of the CNC device through the position detection feedback device and compared with the input command, and the difference is used to control the moving parts. The characteristics are convenient debugging, good system stability, and compact structure, but the error in the mechanical transmission chain cannot be corrected or eliminated. At present, the ball screw nut mechanism has good accuracy and precision retention and a reliable mechanism that eliminates the reverse motion gap, which can meet the needs of most CNC machine tool users. Therefore, it is widely used and becomes the preferred control method.
The closed-loop control system is to install a linear or rotary detection device at the corresponding position of the moving part of the machine tool, and feed back the directly measured displacement or angular displacement to the comparator of the CNC device, compare it with the input command displacement, and control the moving parts with the difference. The advantage is that all links of the mechanical transmission chain are included in the closed loop, and the accuracy depends on the accuracy of the detection device, which exceeds the semi-closed-loop system. The disadvantage is that it is expensive and has strict requirements on the mechanism and transmission chain, otherwise it will cause oscillation and reduce the stability of the system.
An open-loop control system refers to a control method without a position detection feedback device. It is characterized by a simple structure and low price, but it is difficult to achieve rapid control of moving parts. It is widely used in the drive control of small devices with low torque, high precision and medium speed of stepper motors, especially in microelectronics production equipment.
